Abstract: Abstract: Drying is an effective method for the food industry to extend product's shelf life, which makes the moisture content of the food reduce to a certain extent to ensure microbial stability of the product. Compared to traditional air drying method, short and medium wave infrared drying takes shorter time to evaporate moisture. Water plays a critical role in the chemical and enzymatic reactions and alters material properties. Moisture transfer is therefore a governing factor in drying process. However, heat and moisture transfer in fruits and vegetables drying is a complex process. A better understanding of the mechanism of moisture transfer will be helpful to improve product quality and the efficiency of drying process. In order to investigate the changing rules of water characteristics and glass transition temperature in apple slices during short and medium wave infrared drying, low-field nuclear magnetic resonance (LF-NMR), differential scanning calorimetry (DSC) and other instruments were applied in the test. LF-NMR is commonly used to detect changes in water status with the advantages of fast and non-destructive analysis. It can explain the migration of water from microscopic point of view through its relaxation behavior of inner protons. Results showed that short and medium wave infrared temperatures had strong influence on water diffusion, and the ratio of average drying rates under 50, 70 and 90 ℃ was 1:1.5:2.3. Three kind of water states were obtained from the LF-NMR experiments using the Carr-Purcell-Meiboom-Gill (CPMG) pulse sequences, and among the transverse relaxation time (T2), T21 (1-20 ms), T22 (20-200 ms) and T23 (200-1 000 ms) were corresponding to bound water, immobilized water and free water respectively, which implied that the longer the relaxation time, the stronger the water flow. The dramatically decreased content of free water content in vacuoles was accompanied by the sharp increase in the content of immobilized water in the cytoplasm and extra-cellular space, from 7.96% to 46.82%. Subsequently, the content of immobilized water decreased gradually with time increasing. Short and medium wave infrared drying elevated the glass transition temperature (P<0.05) and reduced water activity (P<0.01) appreciably by decreasing the content of immobilized water in apple tissues, which showed high correlation between glass transition temperature or water activity and water status. Obviously shrinkage occurred in apple slices along with the water loss in the process of drying, and volume and moisture content showed a significant correlation (R>0.99). This research provides the theoretical basis for understanding the water diffusion characteristics of short and medium wave infrared drying.